Interpretation of the between-country variance as a function of 'x', random slope

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KazimovHH
Posts: 14
Joined: Mon Apr 09, 2018 11:56 am

Interpretation of the between-country variance as a function of 'x', random slope

Post by KazimovHH » Tue Oct 09, 2018 1:38 pm

Dear Community,

I have difficulties to interpret the results of the between-country variance function.

In the random slope model, I hypothesize that the effect of internal efficacy varies across countries in a relationship with the propensity to vote among young voters. Covariance structure of the model is negative and the graph subsequently shows 'fanning in' pattern. The correlation between the random slope and intercept is negative, -.07904731. Therefore, I expect that the between-country variation will decrease by increasing internal efficacy.

However, the plot shows an increase in between-country variance.

Code: Select all

twoway function [RP2]var(cons) + 2*[RP2]cov(cons\Inteff_c)*x + [RP2]var(Inteff_c)*x^2, range(1 5) ///
	bgcolor(white) graphregion(color(white)) ///
	ytitle("Level 2 variance function") scale(0.7) ///
	xtitle("Internal Efficacy")	
plot.png
between country variance function
plot.png (70.43 KiB) Viewed 1571 times
I assume that the plot shows an increase due to the situation that the coefficient of the quadratic term is larger than the coefficient of the linear term in the variance function to extend that random slope of internal efficacy contributes to the total-between community variance.

Please let me know if you have any suggestions.

Looking forward.
Regards,
Rza

GeorgeLeckie
Site Admin
Posts: 426
Joined: Fri Apr 01, 2011 2:14 pm

Re: Interpretation of the between-country variance as a function of 'x', random slope

Post by GeorgeLeckie » Tue Oct 09, 2018 4:02 pm

Negative covariance means that the variance function will be decreasing when x = 0. It will however, increase again eventually at higher values of x and this is what you see.

Similarly, you will see fanning in at x = 0, but will see fanning out again at higher values of x.

KazimovHH
Posts: 14
Joined: Mon Apr 09, 2018 11:56 am

Re: Interpretation of the between-country variance as a function of 'x', random slope

Post by KazimovHH » Tue Oct 09, 2018 6:40 pm

Dear George,

Thank you very much for the feedback.
Regards,
Rza

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